The invention relates to a method for defining a hierarchy for a system. A system can be represented in a hierarchical fashion from a system level to a subsystem level to a component level, etc. At each level, critical to quality (CTQ) parameters may be defined which represent aspects of the system that are important to meeting various metrics (performance, customer satisfaction, etc.). The concept of xe2x80x9chouses of qualityxe2x80x9d has been used to represent the decomposition of higher level requirements such as critical to quality parameters or CTQ""s into lower level critical to quality parameters such as key control parameters or KCP""s. FIG. 1 depicts a conventional house of quality hierarchy in which high level requirements such as customer requirements are decomposed into lower level characteristics such as key manufacturing processes and key process variables within the manufacturing processes. This hierarchy can also be applied to system design instead of manufacturing to relate system level critical to quality parameters to sub-system critical to quality parameters. For example, in a projector, a system level CTQ parameter may be image quality, which may depend on sub-system level CTQ parameters such a lamp intensity. While the existing hierarchical system representations are useful, it is understood that improvements to such representations are needed.
An exemplary embodiment of the invention is directed to a method for defining a system hierarchy for a system including a plurality of variables. The method includes generating a first level system block corresponding to a first variable at a first level of the system hierarchy. The first level system block includes statistical information related to the first variable. A second level system block is generated corresponding to a second variable at a second level of the system hierarchy. The second variable has an effect on a value of the first variable. The second level system block includes statistical information related to the second variable.